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Epidemics have always been the cause of significant economic and life losses. Among the multiple developments of science against infectious diseases, mathematical and computational models are increasingly important, especially after the development of complexity and network science. The study and forecasting of epidemics are highly influenced by behaviors of host populations, which are unpredictable and difficult to incorporate. In this thesis, we contribute to the substantial volume of works dedicated to solving this problem. First, we approach the coupling between disease and information spreading on multiplex networks. We propose a rumor-like model for the information and a flexible ratio of time scales between disease and information. We show that increasing the time scale of the information reduces the disease prevalence. We also show that stiflers may cause an increase in both infection and information levels. This problem is then further studied with more general models of asymmetrical interaction between contagion phenomena. We show that our previous results on the time scale depend on the form of interaction between the spreading processes. We also study in more depth these models, numerically describing their transient oscillations and deriving analytical expressions for their steady states and phase transitions. We then switch to systems with host mobility, which is an important ingredient of epidemic spreading. We first develop an individual-based mobility and epidemic model, into which behavioral responses are incorporated as an avoidance of infectious hosts. We show how this reduces the disease spreading in different regimes of our model. In particular, for when mobility evolves much faster than epidemics, we derive a semi-analytical approach to describe the model´s bifurcation diagrams, verifying the existence of a bistable region and relating the dynamics to some metrics of the underlying networks. Finally, we move to larger scales and describe mobility as net flows between homogeneous populations. In this metapopulation scheme, we propose a model for behavioral responses that directly reduce the disease reproduction number. We show that our model can generate different outbreak sizes between subpopulations. Then we use it to compare strategies in which each subpopulation responds independently (locally), or the whole population follows the same response curve (globally). We show which strategy is more effective in different scenarios, for both a random geometric graph and two metapopulations constructed from real data. With the variety of topics that we approached, we hope to contribute significantly to the problem of disease-behavior coupling. Epidemias sempre foram a causa de perdas econômicas e vitais significantes. Entre os múltiplos avanços da ciência contra doenças infecciosas, modelos matemáticos e computacionais são cada vez mais importantes, especialmente após o desenvolvimento da ciência de redes e complexidade. O estudo e previsão de epidemias é muito influenciado por comportamentos da população hospedeira, que são imprevisíveis e difíceis de se incorporar. Nesta tese, contribuímos para o grande volume de trabalhos dedicados a resolver esse problema. Primeiramente, abordamos o acoplamento entre a propagação de doenças e informação em redes multiplex. Propomos um modelo de rumor para a informação, bem como uma razão flexível entre as escalas de tempo da doença e da informação. Mostramos que aumentando a escala temporal da informação se consegue uma redução de casos da doença. Também mostramos que stiflers podem aumentar tanto os níveis da informação quanto da doença. Depois estudamos esse problema mais a fundo com modelos mais gerais de interação assimétrica entre fenômenos de contágio. Mostramos que nossos resultados anteriores com a escala de tempo dependem do formato da interação entre os processos de propagação. Também estudamos esses modelos em mais detalhe, descrevendo numericamente suas oscilações transientes e derivando expressões analíticas para os estados estacionários e transições de fase. Mudamos então para sistemas com mobilidade de hospedeiros. Desenvolvemos um modelo de mobilidade individual, em que respostas comportamentais são incorporadas na forma de esquiva de hospedeiros infectados. Mostramos como isso reduz a propagação da doença em diferentes regimes do modelo. Em particular, para quando a mobilidade progride mais rápido que a doença, derivamos uma abordagem semi-analítica para descrever os diagramas de bifurcação, verificando a existência de uma fase biestável e relacionando a dinâmica com algumas métricas das redes subjacentes. Finalmente, descrevemos a mobilidade como fluxos entre populações homogêneas. Nesse esquema de metapopulação, propomos um modelo para respostas comportamentais que diretamente reduzem o número de reprodução. Mostramos que nosso modelo pode gerar surtos de tamanhos diferentes em cada subpopulação. Então o usamos para comparar estratégias em que cada lugar responde de forma independente (localmente) ou em que toda a população segue a mesma curva (globalmente). Mostramos qual estratégia é mais eficiente em diferentes cenários, tanto para um grafo geométrico aleatório quanto para duas metapopulações de dados reais. Com tal variedade de tópicos explorados, esperamos contribuir para o problema da interação doença-comportamento.

Nowadays, one of the challenges we face when carrying out modeling of epidemic spreading is to develop methods to control disease transmission. In this article we study how the spreading of knowledge of a disease affects the propagation of that disease in a population of interacting individuals. For that, we analyze the interaction between two different processes on multiplex networks: the propagation of an epidemic using the susceptible-infected-susceptible dynamics and the dissemination of information about the disease --and its prevention methods-- using the unaware-aware-unaware dynamics, so that informed individuals are less likely to be infected. Unlike previous related models where disease and information spread at the same time scale, we introduce here a parameter that controls the relative speed between the propagation of the two processes. We study the behavior of this model using a mean-field approach that gives results in good agreement with Monte Carlo simulations on homogeneous complex networks. We find that increasing the rate of information dissemination reduces the disease prevalence, as one may expect. However, increasing the speed of the information process as compared to that of the epidemic process has the counter intuitive effect of increasing the disease prevalence. This result opens an interesting discussion about the effects of information spreading on disease propagation., Comment: 9 pages, 6 figures

Despite the advanced stage of epidemic modeling, there is a major demand for methods to incorporate behavioral responses to the spread of a disease such as social distancing and adoption of prevention methods. Mobility plays an important role in epidemic dynamics and is also affected by behavioral changes, but there are many situations in which real mobility data is incomplete or inaccessible. We present a model for epidemic spreading in temporal networks of mobile agents that incorporates local behavioral responses. Susceptible agents are allowed to move towards the opposite direction of infected agents in their neighborhood. We show that this mechanism considerably decreases the stationary prevalence when the spatial density of agents is low. However, for higher densities, the mechanism causes an abrupt phase transition, where a new bistable phase appears. We develop a semi-analytic approach for the case when the mobility is fast compared to the disease dynamics, and use it to argue that the bistability is caused by the emergence of spatial clusters of susceptible agents. Finally, we characterize the temporal networks formed in the fast mobility regime, showing how the degree distributions and other metrics are affected by the behavioral mechanism. Our work incorporates results previously known from adaptive networks into the population of mobile agents, which can be further developed to be used in mobility-driven models., 10 pages and 12 figures

We have developed an approach to continuously load ultracold $^{85}{\mathrm{Rb}}_{2}$ vibrational ground-state molecules into a crossed optical dipole trap from a magneto-optical trap. The technique relies on a single high-power light beam with a broad spectrum superimposed onto a narrow peak at an energy of about $9400\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$. This single laser source performs all the required steps: the short-range photoassociation creating ground-state molecules after radiative emission, the cooling of the molecular vibrational population down to the lowest vibrational level ${v}_{X}=0$, and the optical trapping of these molecules. Furthermore, we probe by depletion spectroscopy and determine that 75% of the ${v}_{X}=0$ ground-state molecules are in the three lowest rotational levels ${J}_{X}=0$, 1, 2. The lifetime of the ultracold molecules in the optical dipole trap is limited to about 70 ms by off-resonant light scattering. The proposed technique opens perspectives for the formation of new molecular species in the ultracold domain, which are not yet accessible by well-established approaches.

One of the major issues in the theoretical modeling of epidemic spreading is the development of methods to control the transmission of an infectious agent. Human behavior plays a fundamental role in the spreading dynamics and can be used to stop a disease from spreading or to reduce its burden, as individuals aware of the presence of a disease can take measures to reduce their exposure to contagion. In this paper, we propose a mathematical model for the spread of diseases with awareness in complex networks. Unlike previous models, the information is propagated following a generalized Maki-Thompson rumor model. Flexibility on the timescale between information and disease spreading is also included. We verify that the velocity characterizing the diffusion of information awareness greatly influences the disease prevalence. We also show that a reduction in the fraction of unaware individuals does not always imply a decrease of the prevalence, as the relative timescale between disease and awareness spreading plays a crucial role in the systems' dynamics. This result is shown to be independent of the network topology. We finally calculate the epidemic threshold of our model, and show that it does not depend on the relative timescale. Our results provide a new view on how information influence disease spreading and can be used for the development of more efficient methods for disease control., Comment: 12 pages, 8 figures

We have developed a technique to produce, manipulate and trap Rb2 molecules with a single optical beam. This beam is generated by a high-power fiber amplifier (50 W of total output power) in the 1060 to 1070 nm range, which is seeded by two light sources: a sharp-band laser and a broadband superluminescent diode. The laser source is tuned to produce Rb2 molecules from an ultracold 85Rb sample via photoassociation. The broadband spectrum vibrationally cool the molecules by optical pumping. This source is spectrally shaped in order to populate the molecules at the fundamental vibrational state ν = 0. The molecular sample is probed by two-photon ionization, promoted by a pulsed dye laser in the 475 to 480 nm range. By scanning the photoassociation laser frequency, we have obtained a photoassociation spectrum of the ν\' = 138 state of the 0+u potential, confirming previous observations. We have also obtained two vibrational spectra of the molecules by varying the ionization laser frequency, in the presence and absence of the broadband source. The comparison between the two spectra, along with ab-initio data, provides evidences that the molecules are optically pumped to the fundamental vibrational state. Desenvolvemos uma técnica para produzir, manipular e aprisional moléculas de Rb2 com um único feixe óptico. Esse feixe é gerado por um amplificador de alta potência (50 W de potência total de saída) na faixa de 1060 a 1070 nm, que é alimentado por duas fontes de luz: um laser banda estreita e um diodo superluminescente banda larga. O laser é sintonizado para produzir moléculas de Rb2 a partir de uma amostra ultrafria de 85Rb via fotoassociação. O espectro banda larga resfria vibracionalmente as moléculas, por bombeamento óptico. Essa fonte de luz tem seu espectro formatado de modo a deixar as moléculas em seu estado vibracional fundamental ν = 0. A amostra molecular é testada por ionização de dois fótons, promovida por um laser de diodo pulsado na faixa de 475 a 480 nm. Variando a frequência do laser de fotoassociação, obtivemos um espectro de fotoassociação do estado ν\' = 138 do potencial 0+u, confirmando observações anteriores. Obtivemos também dois espectros vibracionais das moléculas variando a frequência do laser de ionização, com e sem a fonte banda larga. Uma comparação entre os dois espectros, junto de dados ab-initio, fornece evidências de que as moléculas são opticamente bombeadas para o estado vibracional fundamental.

Here, we describe the development of an inexpensive and versatile manipulation system forin situexperiments in a field emission scanning electron microscope based on a parallel-guiding plate-spring mechanism and low cost materials. The system has been tested for a wide range of applications, such as collecting, moving, and positioning particles, fabricating atomic force microscopy tips based on carbon nanotubes, and characterizing individual nanobjects. The nanomanipulation results demonstrate that there are many opportunities for the use of physical manipulation in the bottom-up approach to fabrication of nanodevices.

The influence of a high-power single-frequency fiber laser on the formation of ultracold 85Rb2 molecules is investigated as a function of its frequency (in the 1062–1070 nm range) in a magneto-optical trap. We find evidence for the formation of ground-state 85Rb2 molecules in low vibrational levels () with a maximal rate of 104 s−1, induced by short-range photoassociation by the fiber laser followed by spontaneous emission. When this laser is used to set up a dipole trap, we measure an atomic loss rate at a wavelength far from the PA resonances, only four times smaller than that observed at a PA resonance wavelength. This work may have important consequences for atom trapping using lasers around the conventional 1064 nm wavelength.

Quantum gases became an important cross-disciplinary tool in contemporary physics. Here we present the development of new methods to produce and control engineered arbitrary optical potentials to create dynamical quantum simulators of condensed matter systems.

The exploitation of the spin in charge-based systems is opening revolutionary opportunities for device architecture. Surprisingly, room temperature electrical transport through magnetic nanowires is still an unresolved issue. Here, we show that ferromagnetic (Co) suspended atom chains spontaneously display an electron transport of half a conductance quantum, as expected for a fully polarized conduction channel. Similar behavior has been observed for Pd (a quasi-magnetic 4d metal) and Pt (a non-magnetic 5d metal). These results suggest that the nanowire low dimensionality reinforces or induces magnetic behavior, lifting off spin degeneracy even at room temperature and zero external magnetic field., 4 pages, 3 eps figs

This paper describes the use of nanomanipulation for deforming, picking up and positioning nano-objects in situ in a field emission scanning electron microscope using an in-house built manipulator. Our experiments demonstrate that physical manipulation can be used in a wide range of different experiments and systems. The scope of possibilities is quite large, from mounting nanodevices to fabricating AFM tips based on CNTs in addition to measuring mechanical and electrical properties of individual nanosystems. Nanomanipulation has a large application potential in physics, chemistry, biology and engineering, rendering possible the idealised bottom-up approach to nanotechnology.